The present invention seeks to improve the efficiency of bandwidth usage in Satellite Digital Audio Radio Services (“SDARS”), such as those provided by Sirius XM Radio, Inc. (“SXM”). It is thus noted that during the initial design phase of legacy SDARS systems, Concatenated Reed-Solomon Convolutional Codes were considered state of the art in Forward Error Correction (FEC) techniques. Since then, great advances have been made on iterative decoding schemes with the introduction of Turbo and LDPC codes, which are now the common practice in all new system designs and standards, such as, for example, 3gpp2, LTE, 802.11, etc. Thus, for example, SXM has taken advantage of these iterative codes by deploying Hierarchical Modulation (“HM”) systems on their legacy systems, thereby achieving an increased throughput of at least 25% over the original legacy design. Various SXM HM systems are described in U.S. Pat. No. 8,184,743, U.S. Pat. No. 9,036,720 and the various patent applications and references described therein, U.S. Pat. No. 8,139,689, and PCT/US2011/000143, now published as WO 2011/094001, the disclosure of each of which is hereby incorporated herein by reference in its entirety. While the addition of HM was a great improvement as regards bandwidth efficiencies, the modulation and FEC coding used (since the beginning) in the legacy systems still present a major roadblock to any further advances in overall bandwidth efficiency. Moreover, any changes made to a legacy system would also need to maintain backwards compatibility with the millions of existing satellite radios in the market.
What is needed in the art are ways to overcome these problems to obtain additional bandwidth without sacrificing backwards compatibility of existing receivers.